In conventional and particular inner-rotor-type motors, a stator and a rotor are included in a state where a plurality of coils is wound around a stator core of the stator, and the rotor is rotated in the stator core. Therefore, the rotor as well as the stator core must be accurately held at predetermined positions. When a housing is provided in order to fix both components, and the stator core as well as the housing are made from the same iron-group materials, the stator core is press-inserted or fitted into the housing, whereby the stator core can be easily fixed to the housing. However, when the both components are made from different materials, for example, iron and aluminum, a fitting configuration, in which a specification environment as well as an influence of self-heating are considered, is required.